The present invention relates to a mechanism for taking up the slack in a web of cleaning material when changing supply and take-up rollers in a fuser section of an electrophotographic copier/printer machine and in one of its aspects relates to a clutch mechanism which allows the take-up roller of a web cleaning assembly to be advanced without actuation of the drive motor whereby any slack in the web between the supply roller and the take-up roller can be removed manually before the machine is put into operation.
In a typical electrophotographic machine (e.g. copier, duplicator, printer, etc.), a continuous loop of photoconductor film is commonly used to transfer an image from an input section onto a receiving medium (e.g. a sheet of paper or the like). The film is charged and passed through an input section where an image (i.e. analog or digital) is projected onto the charged film. The film then moves through a developing section where toner is applied to the charged image before the image is transferred to the sheet of paper. The paper is subsequently passed through a fuser section where the toner is fixed to the paper by passing the paper between two rollers, i.e. a pressure roller and a fuser roller, one of which is heated. For example, it is common to heat the fuser roller by positioning the fuser roller in contact with one or more heater rollers, which in turn, transfer heat to the fuser roller.
A known problem in fuser sections of this type is that known as xe2x80x9coffsetxe2x80x9d which occurs when some of the heat-softened toner particles remain on the fuser roller and are not transferred to the paper as desired. As well understood in the art, this offset can severely affect the quality of the copies being made by the machine. To alleviate this problem, a release oil is typically applied onto the fuser roller to prevent the toner from sticking thereto.
Due to the direct contact between the fuser roller and the heater rollers, the heater rollers also effectively act as cleaning rollers in that they pick up excess release oil along with other contaminants, e.g. residual toner, paper dust, etc., from the fuser roller. In turn, these contaminants must be continuously removed from the heater rollers during the copying operation in order to maintain high quality copies from the machine. Accordingly, most machines of this type now include some means for continuously xe2x80x9ccleaningxe2x80x9d these contaminants off of the heater rollers during the copying operation.
One known way to clean the heater rollers is to provide a xe2x80x9cweb cleaningxe2x80x9d assembly within the fuser section which includes a length or xe2x80x9cwebxe2x80x9d of cleaning material (i.e. woven material such as NOMEX). The web is wound onto a supply roller which is removably positioned within the assembly and continuously contacts and xe2x80x9cwipesxe2x80x9d the contaminants off of the heater rollers as the web is pulled onto a take-up roller which, in turn, is rotated through a set of gears by a drive motor. Since the web material is regularly advanced during the copying operation, the web material on the supply roller will eventually run out and will need to be replaced. That is, both the empty supply roller and the full take-up roller will need to be replaced whenever the supply of web material runs out.
Since these rollers will need to be replaced on a relatively frequent basis, the procedure for changing out the rollers should be as easy and as mistake proof as possible. Preferably, this should be simple enough so that an operator of the machine, vis-à-vis a dedicated service technician, can be given minimal training to perform this task as needed thereby averting a service call each time the web material runs out.
In known machines of this type, the supply and take-up rollers are normally replaced by pulling the web cleaning assembly out from the fuser housing on a slide rail mounted therein. A spring-loaded pin is released at one end of the take-up roller that is then lifted off a pin at the other end. Once one roller (e.g. full take-up roller) is free, the other roller (e.g. empty supply roller) is removed in a similar manner and the respective rollers are replaced by reversing this procedure.
Whenever the supply and take-up rollers are replaced, a certain amount of xe2x80x9cslackxe2x80x9d will remain in the web after the web has been properly xe2x80x9cthreadedxe2x80x9d through its operational path in the cleaning assembly (i.e. from the supply roller, around a tensioning roller and into contact with the heater rollers, and onto the take-up roller). As will be understood in this art, removing this slack after the rollers have been installed is normally difficult to accomplish. If this slack is not removed before the machine is put back into operation, the slackened web can be drawn into the heater rollers which, in turn, is likely to tear the web off of one or the other of the rollers thereby resulting in substantial downtime and expense.
In known machines of this type, this slack is removed from the web by manually rotating the take-up roller to thereby wind up the excess web onto the take-up roller. However, this procedure requires that the drive shaft of the drive motor be manually rotated along with the associated meshed gears which drive the take-up roller. Since the commercially available drive motors commonly used in these machines normally have high gear ratios (i.e. 180 to 1), the manual turning of the motor is extremely difficult to accomplish with the tools normally available to a technician. Accordingly, those skilled in this art will readily recognize the benefits of simplifying the exchange of web supply and take-up rollers in a web cleaning assembly of an electrophotographic machine wherein the slack normally present in the web after such an exchange can easily and quickly be removed by a technician without the need of special tools or assistance.
The present invention provides an electrophotographic apparatus having a fuser section which includes a web cleaning assembly and a method for servicing the web cleaning assembly to take-up the slack in the web cleaning material when the supply and take-up rollers are replaced therein. Basically, a clutch mechanism is positioned between the drive gear on the take-up roller and the hub on the drive shaft of the motor which drives the drive gear. A spring-biased pawl on the hub cooperates with an inner set of teeth on the drive gear to provide a driving connection between the hub and the take-up gear when the motor drives the hub in a first direction but effectively releases the driving connection when the take-up gear is manually rotated while the motor is idle. This allows the take-up roller to be rotated to take up the slack in the web without having to rotate the drive shaft of the motor.
More specifically, the present invention relates to a web cleaning assembly which is adapted to be mounted in the fuser section of an electrophotographic apparatus for cleaning contaminates off of at least one heater roller in the fuser section. The web cleaning assembly includes a frame having a supply roller on which a web of cleaning material is wound and a take-up roller that receives the used cleaning material after the material has contacted and removed contaminants from the heater roller(s) in the fuser section of the apparatus.
A drive gear is drivingly connected to the take-up roller and has a set of outer teeth around its circumference and a set of inner teeth around a central bore therethrough. The central bore is positioned onto a hub, which in turn, is drivingly connected onto the drive shaft of a motor. The hub has a slot in which a pawl is pivotably mounted, the outer end of which is biased outwardly by a spring or the like. The outer end of the pawl engages one of the inner teeth to form a driving connection between the hub and the drive gear wherever the motor drives the hub in a first direction.
A handle extends across the outside of the drive gear and is secured thereto by bolts or the like by which the drive gear can be manually rotated while the motor is idle and the hub is stationary. Since the outer teeth on the drive gear are meshed with the teeth on the take-up gear, the take-up roller can be rotated and any slack in the web material can be taken-up by merely turning the handle on the drive gear without having to turn the drive shaft of the motor. This highly simplifies the removal and installation of the supply and take-up rollers in the web cleaning assembly since the high gear ratio (e.g. 180 to 1) normally found in motors of this type makes the manual turning of motor and associated gears difficult.